This invention relates to the disposal of processing solutions used to process silver halide photographic materials.
Color photographic processing typically includes the processing steps of development, bleaching, fixing, washing and stabilizing. For color negative materials these steps are practiced using a color developer that generates the dye image and, as a side product, metallic silver; a bleach containing a heavy metal bleaching agent that converts any metallic silver into silver ion; and a fixing solution containing a fixing agent that forms soluble silver ion complexes which arc subsequently removed in the washing steps. Finally, the photographic element may be treated to a stabilization step that renders the material stable for storage and includes agents, such as surfactants, that allow water to sheet off the surface without streaking.
The overflow from such a photographic process may consist of environmentally regulated substances such as the reduced form of the color developing agent and its oxidized derivatives, heavy metal ions including silver ion, sequestering agents, and substances that have high oxygen demand. Environmental regulations in some locations restrict the discharge of the reduced form of color developer and solutions which contain any leachable silver greater than 5 ppm. Thus it is typical that this waste is collected in receiver tanks using either one receiver for each solution or one receiver for all solutions. A qualified hauler then picks up the liquid waste for disposal. If the pH of the waste solutions exceeds 12.5 or is less than 2, other environmental regulations may apply.
One alternative to such a xe2x80x9chaul awayxe2x80x9d process by a qualified hauler is to convert the waste by chemical or physical means into a residual solid that can be removed to a place of safe and legal disposal. U.S. Pat. No. 5,457,272 describes a method that solidifies photographic effluent by adding a water-soluble silicate to the effluent in an amount that renders the mixture glass-like and less permeable to water. Unfortunately this reaction occurs over days, which increases the expense to the user because it requires an on-site treatment and storage area. In addition, the effluent cannot contain ammonium ions, since the effluent might release free ammonia when the alkaline earth compound, such as calcium hydroxide, is added. This restriction limits the manufacturer""s formulation options.
U.S. Pat. No. 5,275,509 describes a method of disposing of photographic fixer and developer using an absorbing polymer which is substantially insoluble in the mixture of equal parts fixer and developer. The expectation is that the silver ion in this mixture is immobilized and precipitates as insoluble silver sulfide. The mixture can then be disposed of in a landfill or similar site designed to receive nontoxic waste. This practice, however, when applied to the combined color photographic processing effluent, would not address the issue of the reduced color developing agent. In addition, it has been discovered by the inventors herein that the silver ion is not immobilized by the absorbing polymer but can leach from the absorbent, making the resultant mixture subject to environmental regulation.
One method to reduce the silver ion concentration below 5 ppm is to precipitate it from the solution. A particularly efficient precipitating agent is trimercato-s-triazine (TMT) as described in patents U.S. Pat. Nos. 5,288,278; 5,437,792; 5,476,593; 5,496,474; 5,563,267; 5,759,410; and 5,961,939 and references sited therein. These patents describe how to reduce the silver ion concentration below 5 ppm in effluent mixtures that are then discharged to the drain. No consideration is given to managing the reduced form of the color developing agent or the conversion of the liquid waste to apparently dry waste. Other methods of isolation convert the silver ion to silver metal such as electrolytic reduction or use of galvanic cells such as used in the steel wool containing chemical recovery cartridges.
There is still needed a means of waste disposal of combined waste photoprocessing solutions which is simple, less expensive and which is not subject to environmental regulation.
This invention provides a method of disposing of photographic silver halide processing solutions including developer solution, bleach solution and at least one silver bearing solution comprising a) combining the developer and bleach solutions to oxidize the developing agent in the developer and form a developer/bleach waste solution, b) treating the silver bearing solution(s) to reduce the silver ion level and form a low silver waste solution; and c) contacting the developer/bleach waste solution and the low silver waste solution with an absorbent material to form an apparently dry waste material having a leachable silver ion level below 5 ppm.
The present invention provides a process to use the natural chemistry of the color photographic solution reactions to lower their hazard rating and to add absorbent material to convert the aqueous waste to apparently dry waste. Combining the bleach and developer waste solutions results in the complete oxidation of the reduced developer. Contacting this combined solution with an absorbing material converts the solution to an apparently dry waste that can be discharged to a common waste receptacle. A general hauler can now dispose of this apparently dry, nontoxic waste. This invention also provides the means to reduce the level of leachable silver ion from silver bearing waste solutions to below 5 ppm. The liquid mixture can then be rendered apparently dry and shipped to a refiner to extract the silver. Alternatively, the silver ion can be separately removed from the effluent stream to a level below 5 ppm and the residual liquid rendered apparently dry for easy waste disposal to a landfill or similar site designed to receive nontoxic waste.
The first step in the method of the invention is to combine the overflow or waste developer and bleach solutions to oxidize the developing agents in the developer and form a developer/bleach waste solution. The function of the developer in the photochemical process is to reduce the silver halide in the silver halide photographic material to silver metal. In so doing, the developing agent is oxidized. With color photographic materials, the useful image consists of one or more organic dye images produced by color couplers which react with the oxidized color developing agent formed wherever silver halide is reduced to metallic silver. After the completion of the color developing step the unused color developing agent is in a reduced state.
The function of the bleach bath in the photochemical process is to convert metallic silver formed in the developer to an ionic state. The bleach reaction requires that the silver be oxidized by an oxidizing agent. The overflow or waste bleach solution contains a certain amount of unreacted oxidizing agent. By combining the waste bleach and developer solutions the reduced developer is oxidized to an environmentally benign developer/bleach waste solution. Additionally the pH of the waste developer is often quite high, generally about 9 to 12. Combining it with the bleach solution which generally has a pH of 2 to 6.5 neutralizes the alkaline developer. Combining the bleach and developer may be done in any manner known to those skilled in the art such as by mixing, agitation, spraying or any other means. It may be done at a separate waste processing station with the developer/bleach waste solution then being transported to a waste processing station containing the absorbent or it could be done, for example, by combining the solutions at a processing station and then adding the absorbent at the same station. The waste processing station may be any area wherein a waste solution is processed. The various stations may be part of the same apparatus or piece of equipment or they may be in separate pieces of equipment. They may also be part of the photoprocessing equipment. They may also be in the same or different geographic locations. Nonlimiting examples of waste processing stations include a tank, chamber, channel, or drum.
To render photographic processing effluent non-toxic requires the complete oxidation of the color-developing agent in the waste effluent. As an example, in one embodiment of the invention this can occur according to the following reaction:
CDred+2(iron(III)complex)= greater than CDox+2(iron(II)complex)+2H+
The molar concentrations of the developer in the fresh process solution is often significantly lower than the molar concentrations of the beaching agent in the bleach solution. For example in typical solutions the color developer concentration is 0.077 moles/liter while the iron(III) concentration in the bleach is 0.466 moles per liter. If equal parts of these solutions are mixed together it is expected that the color developing, agent would be completely oxidized. However, during processing these solutions are not used at the same relative rates. The reactions in the developer control the image formation and are therefore sensitive to waste products of the development process. The bleaching solution is often more concentrated and less critical to the imaging process therefore this solution is often used at a lower rate than the developer solution. Ratios vary from as high as 3:1 developer to bleach down to 1:1. At a 3:1 ratio, the formulation of the fresh solutions are just sufficient to stoichiometrically convert the reduced form of the developer (0.23 moles in the above example) to the oxidized form (requires 0.46 moles of iron(III) complex). Therefore, in order to be assured that there is sufficient bleaching agent in its oxidized form to convert the reduced developing agent to its oxidized form requires that the color developer solution and the bleach solution be mixed together before combining with the other process waste streams coming from the fixer and rinse steps. In particular, mixtures of the fixer solution react with the bleaching agent to convert it to iron(II) thereby lowering the available iron(III) to effect complete oxidation of the color developing agent. Incomplete oxidation of the color developer results in a toxic solution.
The developer/bleach waste solution is then contacted with at absorbent material to form an apparently dry waste material. Useful absorbent materials are described in detail below.
The silver-bearing waste solutions, which include but are not limited to fixers, washes and rinses, are treated to reduce the silver ion level and form a low silver waste solution. Preferably the silver ion is reduced to below 5 ppm. It is the amount of silver ion which determines if the waste solution is low silver. The low silver waste solution may contain insoluble silver. The low silver waste solution is then contacted with an absorbent material to form an apparently dry waste material. The apparently dry waste material must have a leachable silver ion concentration below 5 ppm as defined by Method 1311 (xe2x80x94TCLPxe2x80x94Toxicity Characteristic Leaching Procedure), said method incorporated herein by reference. The treatment to reduce the silver ion level and contacting the low silver waste solution may done virtually simultaneously and this invention is intended to include that possibility. For example, in one embodiment the silver bearing solutions are treated to reduce silver ion content by contacting the solutions with a precipitating agent which will precipitate insoluble silver salts. In one variation of that embodiment the absorbent material and the precipitating agent are contained in the same vessel or container so that the silver hearing solutions will come in contact with the precipitating agent almost simultaneously with coming into contact with the absorbent material.
In another variation of the embodiment wherein the silver bearing solutions are treated with a precipitating agent, the solutions are treated prior to being placed in contact with the absorbent. This may be done at a separate waste processing station or it could be done, for example, by treating the solutions with the precipitating agent at a processing station and then adding the absorbent at the same station. In one preferred embodiment the treated silver bearing solution is separated into a low silver waste solution and insoluble silver prior to the solution coining into contact with the absorbent. The isolated silver can be then be sent to the refiner. The absorbed mother liquor from this separation is now apparently dry and can be sent to an appropriate landfill using a general hauler.
The silver bearing solutions may also be treated to reduce silver ion content by converting the silver ion into silver metal. Examples of methods used to convert the silver ion into silver metal include electrolytic reduction which converts silver ion into silver metal using an electric current or the use of a galvanic cell which converts silver ion to silver with iron or aluminum in a chemical recovery cartridge. The treatment to reduce silver ion may also include a combination of treatment with a precipitating agent and treatment to convert silver ion to silver metal.
The silver bearing solutions may be treated separately to reduce silver ion level or they may be combined before being treated to reduce silver ion level. Preferably they are combined. The developer/bleach waste solution and tile low silver waste solution may be treated as two separate waste streams wherein the developer/bleach waste solution is contacted with a first absorbent material and the low silver waste solution is contacted with a second absorbent material resulting in two separate apparently dry waste materials. Alternatively, the developer/bleach waste solution and the low silver waste solution may be treated as one waste stream wherein the developer/bleach waste solution and the low silver waste solution are contacted with the same absorbent material resulting in one apparently dry waste material.
Precipitating agents effective in reducing the silver ion concentration below 5 ppm in photographic waste are known to those skilled in the art. Nonlimiting examples include metal sulfide salts or metal hydrogensulfide salts; a wide variety of alkyl, aryl, and heterocyclic thiol compounds, including mercaptoazoles such as 5-mercaptotetrazoles, mercaptoazines such as mercaptopyridines, mercaptopyrazines, mercaptopyridazines, mercaptopyrimidines; N-substituted dithiocarbamate salts; O-substituted xanthate salts; and tetraazaindenes; purines. One particularly useful class of precipitating agenets are derived from mercapto-s-triazine or water-soluble salts thereof. The mercapto-s-triazine compound has the formula 
wherein:
R is hydrogen, xe2x80x94NH4, xe2x80x94OH, an alkyl having 1 to 8 carbon atoms, an alkoxy having 1-8 carbon atoms, phenyl, cyclohexyl, oxazinyl, phenoxy, xe2x80x94NRxe2x80x22 or xe2x80x94SRxe2x80x3. Rxe2x80x2 is hydrogen, an alkyl having 1 to 8 carbon atoms, phenyl, cyclohexyl, naphthyl or benzyl. Rxe2x80x3 is an alkyl having 1 to 8 carbon atoms, phenyl, cyclohexyl, naphthyl or benzyl, m is an integer from 1 to 3 and n is 0 or all integer from 1 to 2. A preferred embodiment is trimercapto-s-triazine (TMT) which is sold by Degussa under the tradename xe2x80x9cTMT-15xe2x80x9d.
In the following discussion a xe2x80x9cgelxe2x80x9d is a gelatinous colloidal material and xe2x80x9cgelatinxe2x80x9d is protein derived from a collagen source. Absorbent materials which may be useful in the invention can include inorganic materials such as silica gels or organic materials as described below.
Absorbent materials which are preferred for use in this invention are those wherein the absorbent material absorbs at least 20 mls/gm of distilled water using EPA Test Method 9095A, the Paint Filter Liquids Test, said Method incorporated herein by reference and referred to herein as xe2x80x9cthe Paint Filter testxe2x80x9d. More preferred are those absorbent materials which absorb at least 50 mls/gm of distilled water using the Paint Filter test. Most preferred are those absorbent materials which absorb at least 100 mls/gm of distilled water using the Paint Filter test.
One class of particularly useful materials with high absorbing capacity is that of superabsorbent polymers. Most of the superabsorbent gels used today are found in baby and feminine hygiene products, agricultural and horticultural applications, cabling, construction materials, food packaging, radioactive waste, and medical waste management. Superabsorbent polymers are crosslinked networks of flexible polymer chains manufactured usually in the form of granules, beads, or powders.
Based on the nature of the groups attached to the polymer backbone, absorbing polymers can be classified into two main groups ionic and non-ionic. The swelling capability of non-ionic polymers in water is a result of diffusion and solvation of the hydrophilic groups of the polymer, the same mechanism that is responsible for dissolution of water-soluble polymers. The difference is that the crosslinks allow the polymer to keep its shape after absorbing water. In contrast, the driving force for ionic polymers is the solvation of ionic groups (e.g. negatively charged sulfonate or carboxylate groups). These groups are more strongly solvated than non-ionic groups and repel adjacent groups of similar charge in the polymer chain. The requirement for charge neutrality and the associated free counterions and the strong solvation create a strong osmotic force and high swelling capacity for these gels.
Commercially available superabsorbents are lightly crosslinked homopolymers or copolymers of partially neutralized acrylic acid, its derivatives (e.g. acrylamide), or other polymers (e.g. polyalcohols). These materials are usually produced by suspension or bulk polymerization. In order to achieve superabsorbent properties, acrylic acid can be co-polymerized with another monomer containing multiple vinyl groups, so that crosslinks are formed during the polymerization reaction, or polymer chains can be subsequently crosslinked with reaction to a di-functional molecule. Depending on the method, small amounts of crosslinkers or reaction initiators may be added to the reacting mixture and small amounts of monomer and non-crosslinked chains may remain in the final product. Even at ppm level, additives or impurities can have a great effect on the properties of the gel produced. There are infinite possibilities for engineering the properties of such polymers, so they address the needs of a particular application. For a description of superabsorbent materials, their chemistry and manufacturing methods see Modern Superabsorbent Polymer Technology, edited by F. L. Buchholz and A. T. Graham, WILEY-VCH, 1998.
Although superabsorbent gels may absorb over 100 mls of water per gram of gel, their swell performance depends on the molecular structure of the polymer, the degree of crosslinking, the morphology and size of the gel particles and the ionic strength and pH of the solution to be absorbed (D. Dhara, C. K. Nisha, P. R. Chatterji, J. Macromolecular Science, Part Axe2x80x94Pure and Applied Chem, 36, 1999, pp197 to 210. Certain products (e.g. hygiene products as described in U.S. Pat. No. 5,429,629) employ combinations of the above materials (i.e. microfiber matrices with interspersed superabsorbent gel particles) to maximize absorbing capacity and ensure uniform wetting.
For photographic processing waste management, three properties of such gels are important; 1) equilibrium absorption capacity (mls of solution absorbed per gram of gel), and good performance on the Paint Filter test (EPA Test Method 9095A), 2) absorption rate (mls of solution absorbed/gram of gel vs. time); and 3) adequate thermal stability of the swollen absorbent. An absorbent material containing photoprocessing effluent can be discarded in a municipal solid waste landfill, that is the regular trash, if it does not contain free liquids. For purposes of this invention a material is determined to contain free liquids as defined by the EPA Test Method 9095A, the Paint Filter Liquids Test. Apparently dry waste materials are those materials that pass this published test method.
Ideally, gels used for solidifying solution waste should be very fast, efficient and homogeneous absorbers to minimize materials and facilitate packaging and transportation. The absorption rate is critical for systems where large amounts of solutions may be disposed at once (seasoned processors) and are less critical for single-use processors that process and discard small volumes of solution at a time. In addition, since it is required to transport the spent absorbent material (swollen with photographic processing effluent) from the point of waste generation to the point of disposal, the spent absorbent should be stable at the temperatures to which it is subjected to during transportation.
A class of absorbents that is environmentally friendly is made from biodegradable materials. Usual synthetic polymers such as vinyl, urethanes, esters, phenolic resins are not susceptible to bacterial degradation. The two most common polymers that are biodegradable are polysaccharides (degraded to glucose) and proteins (degraded to amino acids) and they are also naturally occurring. The requirement for these materials to be considered absorbents is that they do not xe2x80x9cdissolvexe2x80x9d in the solutions that they are trying to absorb. In order to render them insoluble, it is necessary that they be crosslinked to some degree. These crosslinks can be achieved by using a chemical cross linker such as chrome-alum (that reacts with carboxylic acid sites) or aldehydes (that react with the amine sites in the proteins). It is also possible to crosslink via physical interactions. For example polysaccharide gels from carrageenan, alginates and agar have been well documented and used in the food industry. Similarly protein gels such as from gelatin are also well known.
Although, it is possible to use gels from polysaccharides as absorbents they suffer from two disadvantages. First the gelation of the material is very sensitive to the presence of salts, which can be particularly problematic for absorbing photographic processing effluents. Secondly the absorption capacity of these gels is limited, due to the low amount of ionic species present in these molecules. Gels from gelatin, on the other hand, are thermoreversible and not very susceptible to the presence of ions. Secondly, the presence of high concentration of carboxylic acid groups and amine groups, allows gelatin gels to be crosslinked by chemical means.
The absorption efficiency of gelatin gels are based on two factors 1) the osmotic component of the gel, which is directly proportional to the number of polymer segments that are soluble in water plus the amount of associated counterions, necessary to maintain electroneutrality, due to the charges on the gelatin; and 2) the amount of physical or chemical crosslinks that inhibit the gel from expanding. The only means to manipulate the osmotic component of gelatin is via the amino acid species that are ionizable, specifically those that contain free carboxylic acid (aspartic acid and glutamic acid) and free amines (lysine, hydroxylysine and aspartine). Since, both these species are titratable in the pH ranges of interest, there exists a pH, called the isoelectric point (IEP), at which the number of ionized acid sites equals the number of protonated amine sites, such that the net charge on the gelatin molecule is zero. The charge on the molecule increases as the pH is changed away from the isoelectric point. Thus, it is desirable to choose gelatin materials whose isoelectric point is furthest from the pH of the solution to be absorbed. The isoelectric point of the gelatin depends on the source of the collagen, from which it is made, as well as the conditions of hydrolysis. Gelatins from hides are typically at a higher IEP than from bone. Hydrolysis under acid conditions yield gelatins with a higher IEP than under alkaline conditions. The IEP of some commercial gelatins are listed in the table below:
The modulus of a gelatin gel, is a measure of the amount of physical crosslinks. The modulus is commonly called the bloom strength or gel strength and is one of the properties attributed to the gelatin by the supplier. One method of measuring the gel strength is by chilling a 6.16% gelatin solution to 10 C. for 24 hours and then measuring the weight in grams required to depress a cylindrical plunger 0.5xe2x80x3in diameter, with a {fraction (1/64)}th radius of curvature at the bottom, by 4 mm. The bloom strength is mainly affected by molecular weight of the gelatin and the method of hydrolysis. Harsh hydrolysis and high molecular weight degrade the bloom strength. In order to obtain high absorption efficiency and still maintain integrity of the gelatin an optimum bloom strength is desirable. Thus it is preferred that the gelatin used to prepare an absorbent have a bloom strength between 100 gms and 300 gms.
Since gelatin gels are thermoreversible, the physical crosslinks are usually not enough. This is particularly true when the fully swollen gelatins experience temperatures above 25 C. The melting temperature of a swollen gelatin gel depends on the mean molecular weight of the gelatin and on the amount of water absorbed. It also is affected, to a smaller extent, on the amount and type of the ionic species present in the liquid to be absorbed. One measure of MW is to measure the viscosity of a 6.16% gelatin solution (moisture corrected) adjusted to a pH of 5.75 using Brookfield DV-II viscometer with SC4-18 spindle at 79.4 sxe2x88x921 (60 rpm) at 40xe2x96xa1 C. This viscosity is termed the nominal viscosity of the gelatin and is directly proportional to the mean molecular weight of the gelatin. In order to have a gelatin gel with a high melting point it is desired to have a gelatin whose nominal viscosity is greater than 3 cp. It is especially preferred that the nominal viscosity is greater than 10 cp.
Thus, it is highly desirable to have additional crosslinks achieved via chemical means and which are not thermoreversible. There are several classes of chemical crosslinkers that can be used for gelatin. These are described in xe2x80x9cThe Theory of the Photographic Processxe2x80x9d 4th Ed., Ed. T. H. James, pg. 77-87, 1977. The class of inorganic hardeners are salts of chromium and some salts of aluminum. These typically crosslink via the free carboxylic acids in gelatin and the degree of crosslinking is pH sensitive and also reversible. It is not desirable to use these materials for absorbents because of the impact these materials have on the environment. The organic hardeners act via the xcex5-amino function of lysine and hydroxylysine. There are on the average of 0.35-0.4 mmol of lysine and about 20% of that amount of hydroxylysine per gram of dry gelatin. Classes of organic hardeners include, but are not limited to, aldehydes and blocked aldehydes, ketones, carboxylic and carbamic acid derivatives, sulfonate esters and sulfonyl halides, s-triazines, epoxides, aziridines, isocyanates, carbodiimides and isoxazolitim salts. Polymeric hardeners are generic polymer molecules bearing one or more of the above moieties in their chain. The selection of the hardener type depends on the efficacy of the crosslinking, its toxicity in the native state and the residuals in the absorbent, and cost. The amount of hardener type is a function of the optimization of the absorbents absorption efficiency and thermal stability, as demonstrated in the examples below. For purposes of this invention we define the effective mole of crosslinker as the (number of molecules divided by the Avagadro Number) of the species that can react with two xcex5-amine sites in gelatin. Thus, for a simple hardener like formaldehyde the effective moles is equal to the actual moles, whereas for a polymeric hardener the effective moles is calculated based on the total moles of the monomers that act as crosslinkers. In order to optimize the gelatin absorbent to have a high absorption efficiency and high melting temperature the amount of effective moles of crosslinker should be between 2 and 200 xcexcmole/gm of gelatin.
In order to increase the osmotic component of the gelatin, several other ionic species can be utilized. Ionic polymers, or polyelectrolytes, are preferred because they will not migrate out of the gel. Ionic species are preferred because the osmotic factor is enhanced by the presence of free counterions (in effect more than doubling the osmotic enhancement compared to nonionic species). However, their efficacy is reduced if the absorbing solution also has a high ionic strength. Nevertheless, these polyelectrolytes do provide increased osmotic factor, even for high ionic strength photographic processing effluents, as evidenced in the examples below. The charge on the polyelectrolyte should be opposite to the effective charge on the gelatin molecule and since the IEP of gelatin is usually below 7.0, anionic polyelectrolytes are preferred over cationic ones. Tile anions that are part of the polyelectrolyte may include COOxe2x88x92, SO3xe2x88x92, SO4xe2x88x92, and PO4xe2x88x92. Examples of ionic monomers that comprise these polyelectrolytes are disclosed (but not limited to) in U.S. Pat. Nos. 5,589,322 and 5,977,190. In order to have high compatibility of the polyelectrolytes with gelatin, it is preferred to have polyelectrolytes which have some or all of the anions as COOxe2x88x92, which is common to the anion present on the gelatin molecule. The anionic polyelectrolyte can also be comprised of some amount of nonionic monomer. However, if the amount of anionic monomer is too low, then the absorption efficiency will drop. Thus, it is desired that at least 25% of the monomers be anionic and preferably that these contain a carboxylic acid group. A preferred anionic polyelectrolyte is a polyacrylic acid; particularly useful is sodium poly(acrylamido-2-methyl propane sulfonate).
One of the drawbacks of using polyelectrolytes is that they weaken the gel because they do not participate in physical or chemical crosslinking. One way of overcoming this is to prepare polyelectrolytes that behave like gelatin, except that they have a higher ionic content. These polymers would be ones which have an anionic monomer as well as a cationic monomer that has the same functionality for crosslinking as gelatin. A certain amount of nonionic monomer can also be included to improve the compatibility with gelatin. In order to crosslink effectively, the polyelectrolyte polymer should contain at least 10 mole % of the monomer with the crosslinkable functionality. Examples of such crosslinkable monomers are those that have a quaternary ammonium ion. The amount of polyelectrolyte (not including gelatin) can be up to 50% by weight of the absorbent. The preferred amounts of polyelectrolyte is from 10 to 30% by weight of the absorbent.
The compromise between high osmotic factor and degree of crosslinking depends on the functionality of the absorbent. There is a general relationship that as the efficiency of the absorbent, as defined by milliliters of fluid absorbed per gram of dry absorbent, increases, the melting temperature of the fully swollen absorbent decreases. Although this is a general relationship there are specific combinations of materials that are more favorable than others, as defined by the functionality of the absorbent. As will be shown in the examples below, these novel combinations provide a better thermal stability, for a given degree of absorption efficiency. For purposes of this invention, absorbent effectiveness is defined as the product of the absorbent efficiency (mls of solution absorbed/gm of absorbent) and the melting temperature of the absorbent fully saturated with the respective solution to be absorbed.
Certain absorbents are commercially available absorbents in the form of mats, pads, rolls are usually made of polypropylene or mixtures of polypropylene, polyester microfibers or other similar polymers that can be spun into fibers and woven into a textile form. These materials are mainly used for chemical and petroleum products spill containment. They are lightweight, incinerable, and easier to handle than granular sorbents. Capillary action is the driving force that draws liquids into the fibrous matrix. Manufacturers (e.g. 3M) claim high absorbing capacities for these materials, which have found widespread uses in machine shops, chemical laboratories, petroleum industry, and trucking industry. It has been found such absorbents are not particularly useful when used alone with this invention; however, such absorbents may be useful in combination with the superabsorbents and gelatin gels described above.
Examples that demonstrate this invention use color negative process solutions but are not meant to limit this application to color negative film processing solutions Other photographic materials and processing systems are described in:
Research Disclosure, September 1994, Item 36544, Sections XV to XX which describes supports, exposure, development systems and processing methods and agents and in
Research Disclosure, February 1995, Item 37038 which describes certain desirable photographic elements and processing steps, particularly those useful in conjunction with color reflective prints.
Photographic color developing compositions, the waste solutions of which may be disposed of pursuant to this invention, typically include one or more color developing agents and various other conventional addenda including preservatives or antioxidants (including sulfites, and hydroxylamine and its derivatives), sulfites, metal ion sequestering agents, corrosion inhibitors and buffers. These materials can be present in conventional amounts. For example, the color developing agent is generally present in an amount of at least 0.001 mol/l (preferably at least 0.01 mol/l), and an antioxidant or preservative for the color developing agent is generally present in an amount of at least 0.0001 mol/l (preferably at least 0.001 mol/1). The pH of the composition is generally from about 9 to about 13, and preferably from about 11.5 to about 12.5.
Exemplary color developing compositions and components (except the sensitizing dye stain reducing agents described herein) are described for example, in EP-A-0 530 921 (Buongiorne et al), U.S. Pat. No. 5,037,725 (Cullinan et al), U.S. Pat. No. 5,552,264 (Cullinan et al), U.S. Pat. No. 5,508,155 (Marrese et al), U.S. Pat. No. 4,892,804 (Vincent et al), U.S. Pat. No. 4,482,626 (Twist et al), U.S. Pat. No. 4,414.307 (Kapecki et al), in U.S. Pat. No. 4,876,174 (Ishikawa et al), U.S. Pat. No. 5,354,646 (Kobayashi et al) and U.S. Pat. No. 4,264,716 (Vincent et al), all incorporated herein for their teaching about color developing compositions.
Useful preservatives in the color developing compositions include sulfites (such as sodium sulfite, potassium sulfite, sodium bisulfite and potassium metabisulfite), hydroxylamine and its derivatives, especially those derivatives having substituted or unsubstituted alkyl or aryl groups, hydrazines, hydrazides, amino acids, ascorbic acid (and derivatives thereof), hydroxamic acids, aminoketones, mono- and polysaccharides, mono- and polyamines, quaternary ammonium salts, nitroxy radicals, alcohols, and oximes. More particularly useful hydroxylamine derivatives include substituted and unsubstituted monoalkyl- and dialkylhydroxylamines (especially those substituted with sulfo, carboxy, phospho, hydroxy, carbonamido, sulfonamido or other Solubilizing groups). Mixtures of compounds from the same or different classes of antioxidants can also be used if desired.
Examples of useful antioxidants are described for example, in U.S. Pat. No. 4,892,804 (noted above), U.S. Pat. No. 4,876,174 (noted above), U.S. Pat. No. 5,354,646 (noted above), U.S. Pat. No. 5,660,974 (Marrese et al), and U.S. Pat. No. 5,646,327 (Bums et al), the disclosures of which are all incorporated herein by reference for description of useful antioxidants. Many of these antioxidants are mono- and dialkylhydroxylamines having one or more substituents on one or both alkyl groups. Particularly useful alkyl substituents include sulfo, carboxy, amino, sulfonamido, carbonamido, hydroxy and other solubilizing substituents.
Most preferably, the noted hydroxylamine derivatives can be mono- or dialkylhydroxylamines having one or more hydroxy substituents on the one or more alkyl groups. Representative compounds of this type are described for example in U.S. Pat. No. 5,709,982 (Marrese et al), incorporated herein by reference. Specific di-substituted hydroxylamine antioxidants include, but are not limited to: N,N-bis(2,3-dihydroxypropyl)hydroxylamine, N,N-bis(2-methyl-2,3-dihydroxypropyl)hydroxylamine and N,N-bis(1-hydroxymethyl-2-hydroxy-3-phenylpropyl)hydroxylamine. The first compound is preferred.
Particularly useful color developing agents include aminophenols, p-phenylenediamines (especially N,N-dialkyl-p-phenylenediamines) and others which are well known in the art, such as EP 0 434 097A1 (published Jun. 26, 1991) and EP 0 530 921A1 (published Mar. 10, 1993). Preferred color developing agents include, but are not limited to, N,N-diethyl p-phenylenediamine sulfate (KODAK Color Developing Agent CD-2), 4-amino-3-methyl-N-(2-methane sulfonamidoethyl)aniline sulfate, 4-(N-etyl-N-xcex2-hydroxyethylamino)-2-methylaniline sulfate (KODAK Color Developing Agent CD-4), p-hydroxyethylethylaminoaniline sulfate, 4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediamine sesquisulfate (KODAK Color Developing Agent CD-3), 4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediamine sesquisulfate, and others readily apparent to one skilled in the art.
Photographic bleaching compositions, the waste solutions of which may be disposed of pursuant to this invention, generally include one or more persulfate, peracid (such as hydrogen peroxide, periodates or percarbonates) or high metal valent ion bleaching agents, such as iron(II) complexes with simple anions (such as nitrate, sulfate, and acetate), or with carboxylic acid or phosphonic acid ligands. Particularly useful bleaching agents include iron complexes of one or more aminocarboxylic acids, aminopolycarboxylic acids, polyaminocarboxylic acids or polyaminopolycarboxylic acids, or salts thereof. Particularly useful chelating ligands include conventional polyaminopolycarboxylic acids including ethylenediaminetetraacetic acid, and others described in Research Disclosure, noted above, U.S. Pat. No. 5,582,958 (Buchanan et al) and U.S. Pat. No. 5,753,423 (Buongiorne et al). Biodegradable chelating ligands are also desirable because the impact on the environment is reduced. Useful biodegradable chelating ligands include, but are not limited to, iminodiacetic acid or an alkyliminodiacetic acid (such as methyliminodiacetic acid), ethylenediaminedisuccinic acid and similar compounds as described in EP-A-0 532,003, and ethylenediamine monosuccinic acid and similar compounds as described in U.S. Pat. No. 5,691,120 (Wilson et al), all of which are incorporated herein by reference in relation to their description of bleaching agents.
These and many other such complexing ligands known in the art including those described in U.S. Pat. No. 4,839,262 (Schwartz), U.S. Pat. No. 4,921,779 (Cullinan et al), U.S. Pat. No. 5,037,725 (noted above), U.S. Pat. No. 5,061,608 (Foster et al), U.S. Pat. No. 5,334,491 (Foster et al), U.S. Pat. No. 5,523,195 (Darmon et al), U.S. Pat. No. 5,582,958 (Buchanan et al), U.S. Pat. No. 5,552,264 (noted above), U.S. Pat. No. 5,652,087 (Craver et al), U.S. Pat. No. 5,928,844 (Feeney et al) U.S. Pat. No. 5,652,085 (Wilson et al), U.S. Pat. No. 5,693,456 (Foster et al), U.S. Pat. No. 5,834,170 (Craver et al), and U.S. Pat. No. 5,585,226 (Strickland et al), all incorporated herein by reference for their teaching of bleaching compositions. The total amount of bleaching agent(s) in the composition is generally at least 0.0001 mol/l, and preferably at least 0.05 mol/l. These amounts would apply to bleach-fixing compositions also.
Other components of the bleaching solution include buffers, halides, corrosion inhibiting agents, and metal ion sequestering agents. These and other components and conventional amounts are described in the references in the preceding paragraph. The pH of the bleaching composition is generally from about 4 to about 6.5.
Particularly useful bleaching agents are ferric ion complexes of one or more of ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS, particularly the S,S-isomer), methyliminodiacetic acid (MIDA) or other iminodiacetic acids, beta-alaninediacetic acid (ADA), ethylenediaminemonosuccinic acid (EDMS), 1,3-propylenediaminetetraacetic acid (PDTA), nitrilotriacetic acid (NTA), and 2,6-pyridinedicarboxylic acid (PDCA). The most preferred bleaching agent is a ferric ion complex of EDTA for processing color reversal materials. For processing, color negative materials and color papers, a ferric complex of PDTA is preferred. Multiple bleaching agents can be present if desired.
Fixing solutions, the silver bearing waste solutions of which may be disposed of pursuant to this invention, contain a photographic fixing agent. Examples of photographic fixing agents include, but are not limited to, thiosulfates (for example sodium thiosulfate, potassium thiosulfate and ammonium thiosulfate), thiocyanates (for example sodium thiocyanate, potassium thiocyanate and ammonium thiocyanate), thioethers (such as ethylenebisthioglycolic acid and 3,6-dithia-1,8-octanediol), imides and thiourea. Thiosulfates and thiocyanates are preferred, and thiosulfates are more preferred. Ammonium thiosulfate is most preferred. The general amount of total fixing agents in the fixing composition of this invention is at least 0.001 mol/l, and preferably at least 0.1 mol/l. These amounts would apply to bleach-fixing compositions also.
It is also known to use fixing accelerators in fixing compositions. Representative fixing accelerators include, but are not limited to, ammonium salts, guanidine, ethylenediamine and other amines, quaternary ammonium salts and other amine salts, thiourea, thioethers, thiols and thiolates. Examples of useful thioether fixing accelerators are described in U.S. Pat. No. 5,633,124 (Schmittou et al), incorporated herein for the teaching of fixing compositions.
Fixing compositions generally contain one or more monovalent or divalent cations supplied by various salts used for various purposes (for example, salts of fixing agents). It is preferred that the cations be predominantly ammonium cations, that is at least 50% of the total cations are ammonium ions. Such fixing compositions are generally known as xe2x80x9chigh ammoniumxe2x80x9d fixing compositions.
Fixing compositions can also include one or more of various addenda optionally but commonly used in such compositions for various purposes, including hardening agents, preservatives (such as sulfites or bisulfites), metal sequestering agents (such as polycarboxylic acids and organophosphonic acids), buffers, and fixing accelerators. The amounts of such addenda in the working strength compositions would be readily known to one skilled in the art.
The desired pH of fixing compositions is generally 8 or less, and can be achieved and maintained using any useful combination of acids and bases, as well as various buffers.
Other details of fixing compositions not explicitly described herein are considered well known in the art, and are described for example, in Research Disclosure publication 38957 (noted below), and publications noted therein in paragraph XX(B), U.S. Pat. No. 5,424,176 (Schmittou et al), U.S. Pat. No. 10 4,839,262 (noted above), U.S. Pat. No. 4,921,779 (noted above), U.S. Pat. No. 5,037,725 (noted above), U.S. Pat. No. 5,523,195 (noted above), U.S. Pat. No. 5,552,264 (noted above), all incorporated herein by reference for their teaching of fixing compositions.
Another photoprocessing composition which may result in a silver bearing waste solution is a dye stabilizing composition containing one or more photographic imaging dye stabilizing compounds. Such compositions can be used at the end of the processing sequence (such as for color negative films and color papers), or in another part of the processing sequence (such as between color development and bleaching as a pre-bleaching composition).
Such dye stabilizing compositions generally have a pH of from about 5.5 to about 8, and include a dye stabilization compound (such as an alkali metal formaldehyde bisulfite, hexamethylenetetramine, various benzaldehyde compounds, and various other formaldehyde releasing compounds), buffering agents, bleach-accelerating compounds, secondary amines, preservatives, and metal sequestering agents. All of these compounds and useful amounts are well known in the art, including U.S. Pat. No. 4,839,262 (noted above), U.S. Pat. No. 4,921,779 (noted above), U.S. Pat. No. 5,037,725 (noted above), U.S. Pat. No. 5,523,195 (noted above) and U.S. Pat. No. 5,552,264 (noted above), all incorporated herein by reference for their teaching of dye stabilizing compositions. Generally, one or more photographic dye stabilizing compounds are present in an amount of at least 0.0001 mol/l. A preferred dye-stabilizing composition includes sodium formaldehyde bisulfite as a dye stabilizing compound, and thioglycerol as a bleach-accelerating compound. More preferably, this composition is used as a pre-bleaching composition during the processing of color reversal photographic materials.
In some systems a dye stabilizing composition or final rinsing composition is used to clean the processed photographic material as well as to stabilize the color image. Either type of composition generally includes one or more anionic, nonionic, cationic or amphoteric surfactants, and in the case of dye stabilizing compositions, one or more dye stabilizing compounds as described above. Particularly useful dye stabilizing compounds useful in these dye stabilizing compositions are described for example in EP-A-0 530 832 (Konia et al) and U.S. Pat. No. 5,968,716 (McGuckin et al). Other components and their amounts for both dye stabilizing and final rinsing compositions are described in U.S. Pat. No. 5,952,158 (McGuckin et al), U.S. Pat. No. 3,545,970 (Giorgianni et al), U.S. Pat. No. 3,676,136 (Mowrey), U.S. Pat. No. 4,786,583 (Schwartz), U.S. Pat. No. 5,529,890 (McGuckin et al), U.S. Pat. No. 5,578,432 (McGuckin et al), U.S. Pat. No. 5,534,396 (noted above), U.S. Pat. No. 5,645,980 (McGuckin et al), U.S. Pat. No. 5,667,948 (McGuckin et al), U.S. Pat. No. 5,750,322 (McGuckin et al) and U.S. Pat. No. 5,716,765 (McGuckin et al), all of which are incorporated by reference for their teaching of such compositions.
General and preferred concentrations of the compounds in various compositions are described below in TABLE I. The endpoints of all ranges are considered approximate so that they should be interpreted as xe2x80x9caboutxe2x80x9d the noted amounts.
Representative sequences for processing various color photographic materials are described for example in Research Disclosure publication 308119, December 1989, publication 17643, December 1978, and publication 38957. September 1996.
Silver halide photographic elements which are processed include color negative photographic films, color reversal photographic films, and color photographic papers. The general sequence of steps and conditions (times and temperatures) for processing are well known as Process C-41 and Process ECN-2 for color negative films, Process E-6 and Process K-14 for color reversal films. Process ECP for color prints, and Process RA-4 for color papers.
For example, color negative films that can be processed using the compositions described herein include, but are not limited to, KODAK MAX(trademark) films. KODAK ROYAL GOLD(trademark) films, KODAK GOLD(trademark) films, KODAK PRO GOLD(trademark) films, KODAK FUNTIME(trademark), KODAK EKTAPRESS PLUS(trademark) films, EASTMAN EXR(trademark) films, KODAK ADVANTIX(trademark) films, FUJI SUPER G Plus films, FUJI SMARTFILM(trademark) products, FUJICOLOR NEXIA(trademark) films, KONICA VX films. KONICA SRG3200 film, 3M SCOTCH(trademark) ATG films, and AGFA HDC and XRS films. Films processed can also be those incorporated into what are known as xe2x80x9csingle-use camerasxe2x80x9d.
In addition, color papers that can be processed include, but are not limited, KODAK EKTACOLOR EDGE V, VII and VIII Color Papers (Eastman Kodak Company), KODAK ROYAL VII Color Papers (Eastman Kodak Company), KODAK PORTRA III, IIIM Color Papers (Eastman Kodak Company), KODAK SUPRA III and IIIM Color Papers (Eastman Kodak Company), KODAK ULTRA III Color Papers (Eastman Kodak Company), FUJI SUPER Color Papers (Fuji Photo Co., FA5, FA7 and FA9), FUJI CRYSTAL ARCHIVE and Type C Color Papers (Fuji Photo Co.), KONICA COLOR QA Color Papers (Konica, Type QA6E and QA7), and AGFA TYPE II and PRESTIGE Color Papers (AGFA). The compositions and constructions of such commercial color photographic elements would be readily determined by one skilled in the art, KODAK DURATRANS, KODAK DURACLEAR, KODAK EKTAMAX RAL and KODAK DURAFLEX photographic materials. and KODAK Digital Paper Type 2976 are also typically processed as described above.
The following examples are intended to illustrate and not to limit the invention herein.